| 摘要 |
PROBLEM TO BE SOLVED: To reduce a gap between a small round hole and a core pin by making the core pin using a material having a greater coefficient of linear expansion than that of a piece. SOLUTION: A core pin 26 is made using a material having a greater coefficient of linear expansion than that of a piece 16. During molding, a mold is preheated to increase the temperatures of the piece 16 and the core pin 26. The temperature of the core pin 26 inserted into a small round hole 18 increases by heat conduction through the piece 16. Owing to the difference of the coefficients of linear expansion, the core pin 26 expands greater than the piece 16 to reduce the gap between the core pin 26 and the hole 18. After molding, due to the temperature decrease of the mold, the gap is restored to enable the extraction of the core pin 26. In this way, since the gap between the core pin 26 and the hole 18 is reduced greatly during molding, the dispersion of fiber hole positions of the molding can be reduced. |
